In a groundbreaking experiment conducted in 2021, researchers have achieved a significant milestone in space reproduction, demonstrating that mouse embryos can progress to an early stage of development in the unique conditions of space. The study, detailed in the journal iScience on October 27, involved thawing and growing a few hundred frozen two-cell embryos from mice over four days aboard the International Space Station (ISS). Upon return to Earth, nearly a quarter of the embryos formed healthy clusters of cells known as blastocysts.
The results challenge previous assumptions about the potential hindrances posed by radiation and weightlessness in space to mammalian reproduction. The study, however, only isolates a specific aspect of the reproduction and development process, as blastocysts typically form after fertilization and implant in the uterus before developing into the placenta and fetus.
Space biologist Christiane Hahn, not involved in the research, emphasizes the significance of this breakthrough, noting that mouse embryos are the first mammal embryos successfully grown in space. This achievement marks a crucial step in comprehending how space conditions impact human reproduction, differentiating it from previous experiments involving animals such as salamanders, rice fish, and quail.
Previous research had suggested that the early stages of reproduction in mice could be particularly vulnerable to space conditions. Stress in space often hindered mating, and heavy radiation led to mutations in the rodents’ eggs. However, freeze-dried mouse sperm had previously remained viable after an extended stint on the space station.
To overcome these challenges, biologist Teruhiko Wakayama and his team launched two-cell embryos to the ISS, employing a specially designed device to protect the fragile, developing cells. Of the 360 samples sent, 72 survived the journey, with 17 developing into normal blastocysts. Undamaged cells successfully multiplied, assuming roles as precursors of fetal tissue or the placenta.
While acknowledging the success, Wakayama suggests that future adjustments to the procedure could enhance the success rate, as the absence of perfectly sterile conditions in space likely contributed to cell death. Blastocysts, however, cannot survive for an extended period outside uteruses, limiting the experiment’s duration to a few days.
The researchers express interest in further experiments, including implanting viable embryonic cells from space experiments into mice to observe their development. Additionally, the team aims to investigate the impact of microgravity on the positioning of different cells in a blastocyst, crucial for understanding the potential effects on fetal development, including the occurrence of identical twin mice. While three-quarters of fetal precursors in the study settled correctly, more research is needed to fully comprehend the impact of microgravity on developing cells.
